Conventionally, a group III nitride semiconductor containing a group III element such as aluminum (chemical symbol: Al), gallium (chemical symbol: Ga), indium (chemical symbol: In) or the like, such as aluminum nitride (AlN), gallium nitride (GaN), gallium indium nitride (compositional formula: GaXIn1-XN, 0≦X<1) or the like as a constituent element has been used to configure a group III nitride semiconductor light-emitting element, such as a light-emitting diode (LED) or a laser diode (abbreviation: LD) (refer to Patent Document 1).
For example, in an LED, a gallium indium nitride layer is utilized as a light-emitting layer for emitting visible light of dark green color or blue color (refer to Patent Document 1). Moreover, for example, it is indicated that a Ga0.4In0.6N layer, in which zinc (chemical symbol: Zn) is added (doping is performed) and indium is large in composition, is useful as a material for emitting red light (refer to Patent Document 1). Further, a gallium indium nitride layer, in which indium is small in composition, is used as a light-emitting layer for emitting ultraviolet light (refer to Patent Document 2).
As the conventional visible light LED or the ultraviolet light LED is viewed in terms of a laminated structure, a double hetero (abbreviation: DH) structure of pn junction type is common, in which, for example, a light-emitting layer constituted by an n-type gallium indium nitride layer is arranged on an n-type cladding layer composed of gallium nitride, and further, for example, a p-type cladding layer composed of an aluminum gallium nitride (compositional formula: AlδGaεN, 0≦δ≦1, 0≦ε≦1, δ+ε=1) layer is laminated thereon (refer to Non-Patent Document 1).
In the gallium indium nitride layer used for a light-emitting layer of an LED having such a structure, impurities are intentionally added, that is, a so-called doping is carried out in some cases for adjusting conduction resistance of a current that drives the LED. As n-type impurities in the group III nitride semiconductor, silicon (chemical symbol: Si), germanium (chemical symbol: Ge), tellurium (chemical symbol: Te) and selenium (chemical symbol: Se) are exemplified (refer to paragraph [0008] in Patent Document 3). Germanium is also used as a dopant in manufacturing a layered substance constituted by the group III nitride semiconductors having different atomic concentrations (refer to Patent Document 4). In addition to germanium, in Patent Document 5, sulfur (chemical symbol: S) is described as the n-type impurity (refer to paragraph [0022] in Patent Document 5).